WASHINGTON (AP) — Federal inspection teams have been conducting spot safety checks of rail shipments of crude oil from the booming Bakken oil region in Great Plains states in response to last month’s rail disaster in Canada, U.S. officials said Thursday.

The official name of the inspections is “Operation Classification,” although Cynthia Quarterman, head of the Pipeline and Hazardous Materials Safety Administration, said she prefers to call them the “Bakken Blitz.” They are being carried out jointly with the Federal Railroad Administration and began last weekend, although they weren’t publicly disclosed until Thursday.

Last month, an unattended train carrying oil from the Bakken region came loose and derailed, sending tank cars hurtling into the center of the lakeside Quebec town of Lac-Megantic near the Maine border. Several cars exploded, killing 47 people and destroying much of the town.

Officials said they were surprised by the disaster because they thought the type of oil being transported was unlikely to ignite.

Safety regulations for the transport of crude oil differ depending upon the type of oil and its flashpoint — the lowest temperature at which it will ignite, Quarterman said. Inspectors want to determine whether the quality of the oil being shipped “is what the shipping papers say it is,” said Quarterman, who spoke to reporters at a rail safety meeting.

The Bakken region is a rock formation underlying portions of Montana and North Dakota in the U.S., and Saskatchewan and Manitoba in Canada.

In the first half of this year, U.S. railroads moved 178,000 carloads of crude oil. That’s double the number during the same period last year and 33 times more than during the same period in 2009. The Railway Association of Canada estimates that as many as 140,000 carloads of crude oil will be shipped on Canada’s tracks this year, up from 500 carloads in 2009.

Much of that increase is from oil produced in the Bakken region. The train that crashed in Quebec was carrying oil from North Dakota to a refinery in New Brunswick, Canada.